Halve the butternut squash and place the halves face down on a cookie sheet which has been greased. Bake at 425F for 40 minutes or until the flesh is tender throughout.
While the squash is roasting, heat the margarine in a large saucepan and sauté the onions and ginger until the onions are translucent. Add the broth and simmer for 15 minutes.
Make sure the squash is cooled completely, then scoop the flesh into a blender, along with the broth mixture. I suggest you do this in small batches.
return the pureed soup to the saucepan to bring back to temperature and season with salt and pepper. if the consistency is too thick, add as much water necessary to reach the thickness you desire.
serve with sour cream and enjoy!